Grounded electrical plug construction



Aug. 11, 1964 M. MORSE 3,144,287

GRQUNDED ELECTRICAL PLUG CONSTRUCTION Filed July 3, 1962 United States `Patent O 3,144,287 GROUNDED ELECTRICAL PLUG CONSTRUCTION Milton Morse, 41 Honeek St., Englewood, NJ. Filed July 3, 1962, Ser. No. 207,270 4 Claims. (Cl. 339-14) This invention relates generally to the field of grounded electrical plugs of the type commonly employed for connecting an electrical appliance to a wall or other outlet. Devices of the instant type are generally known in the art, and the invention lies in the specific constructional details.

In devices of this type, there are normally two power prongs provided which extend outwardly of a plug body, and a third or grounding prong positioned to engage a corresponding opening in the electrical outlet with which it is engaged. To enable the grounding prong to be moved out of the Way, where no such corresponding opening is provided, it is known in the art to mount the grounding prong for rotation about a pivotal axis normal to the axis of the grounding prong. It is desirable that the grounding prong be resiliently urged to a position in which the grounding prong axis is parallel to the power prong axes, although the axis may be displaced, wherein the grounding prong will resiliently press against a metallic plate surrounding the outlet to also effect a ground at the point of contact.

Early constructions, as, for example, my prior Patent No. 2,876,426, granted March 3, 1959, accomplish this end, but suffer from a disadvantage in that the resilient element is externally disposed, and thus subject to damage with continued use, as well as accidental disconnection of the resilient element from the grounding prong. Later constructions, as, for example, my prior Patent No. 2,897,469, granted July 28, 1959, avoid this difficulty but make use of rubber resilient elements molded integrally with the plug body, which are subject to fatigue with continued use with the grounding prong in a deflected condition. The molded rubber type of plug presents many advantages, among them being greater resistance to damage and a more attractive appearance, as well `as lower cost of production.

I-t is among the objects of the present invention to provide an improved molded grounding-type plug of the class described, in which the above-mentioned disadvantages have been substantially eliminated.

Another object of the invention lies in the provision of an improved molded grounding electrical plug, in which means is provided for the accommodation of a spring metal resilient element installed therein, in such manner as to be shielded from damage, and which may be readily replaced if necessary.

Another object of the invention lies in the provision of an improved self-grounding molded rubber plug, possessed of the above advantages, in which the cost of fabrication may be of a reasonably low order, with consequent wide sale, distribution and use.

Still another object of the invention lies in the provision of a molded electrical plug which may have an unusually attractive appearance, thereby suiting the device for use in conjunction with household as well as industrial appliances.

A feature of the invention lies in the relative ease with which the grounding prong element may be interconnected with the plug body during assembly thereof.

These objects and features, as well as other incidental ends and advantages, will more fully appear in the progress of the following disclosure, and be pointed out in the appended claims.

In the drawing, to which reference will be made in the specification, similar reference characters have been ern- 3,144,287 Patented Aug. 11, 1964 "ice ployed to designate corresponding parts throughout'the several views.

FIGURE 1 is a fragmentary side elevational View of an embodiment of the invention.

FIGURE 2 is an end elevational view thereof.

FIGURE 3 is a side elevational view thereof partially in section, as seen from plane 3-3 in FIGURE 4 showing the side opposite that seen in FIGURE 1.

FIGURE 4 is an end elevational view thereof, partly broken away in section showing the side opposite that seen in FIGURE 2.

FIGURE 5 is a bottom plan view thereof, partly in section.

In accordance with the invention, the device, generally indicated by reference character 10, comprises broadly: a molded plug body element 11, first and second power prong elements 12 and 13, a grounding prong element 14, and grounding prong actuating means 15.

The molded plug body element 11 is preferably formed from natural or synthetic rubber, although other suitable resilient materials may be employed. The element A11 is bounded by a first end surface 17, an upper peripheral curved surface 18, symmetrical side surfaces 19 and 20, a third side surface 21 having a recess 22 therein, curved surfaces 23 and 24, and angularly-disposed surfaces 25 and 26 on either side of a planar surface 27. Extending through the body element 11 is a transversely-arranged bore 28 which communicates with a cutaway portion or notch 29. The notch 29 includes a quasi-cylindrical portion 30 axially arranged with respect to the bore 28, and a sector portion 31, as best seen in FIGURE 1 in the drawing. The sector portion 31 is bounded by surfaces 32, 33, and 34 to define a space in which the grounding prong element 14 is movable.

The rst and second power prong elements 12 and 13, respectively, may be of a type generally well-known in the art, including an inner end (not shown) having an orifice for the engagement of an electrical conductor 38, and an outer end 40 which may be of slightly tapered configuration to permit easy insertion into a receptacle (not shown).

The grounding prong element 14 is of metallic construction, and includes a tubular bushing 44 and a grounding prong 45. The bushing 44 is positioned within the bore 28 to be resiliently maintained thereby, and includes first and second ends 47 and 48, respectively, an outer surface 39, which may be knurled to provide a secure fit within the body element 11, and an inner surface 49 which is preferably smooth to permit easy movement of the prong 45 therein.

The grounding pro-ng 45 includes an axial portion 50 and a radial portion 51 interconnected by a bend portion 52. This may be formed from copper or brass tubular stock, the forming of which may be a partial screw machine operation. The axial portion 50 is disposed within the bushing 44, and includes a first end portion 54, and a second end portion 55 having a groove 56 milled therein, the bottom surface 57 of which is disposed at an angle with respect to the axis of the radial portion 51 to predetermine the relatively unstressed location of the grounding prong. The bend portion 52 includes a small shelf 59 formed as a result of stamping operations, which shelf serves as a positioning means for the axial portion 50.

The radial portion 51 includes an outer chamfered end 60 to facilitate engagement with a corresponding recess in an outlet (not shown).

The grounding prong yactuating means 15 is in the form of a wire spring, which is resiliently maintained within the recess 22. The recess 22 includes a bottom wall 62, an end wall 63, side walls 64 and 65, and a curved end wall 66. Overlying a portion of the side walls 64 and 65 are retaining lips 67 and 68, respectively, while a circular projection 69 extends outwardly from the bottom wall 62 adjacent the curved end Wall 66.

The means 15 is integrally formed, to include a first rectilinear portion 70, a bend portion 71, a second rectilinear portion 72, a bend portion 73, a third rectilinear portion 74, a curved portion 75, and a fourth rectilinear portion 76, the end 77 of which is disposed within the groove 56 to contact the surface 57. It will be observed that the engagement of the means 15 beneath the lips 67 and 68 is sufficient to retain the means 15 within the recess 22, and the engagement of the end 77 within the groove 56 prevents disengagement of the grounding prong 45 within the bushing 44. As all of the means 15 is disposed beneath the surface 21, the same is substantially shielded from damage or contact with any adjacent object. During the defiecting of the grounding prong, the fourth rectilinear portion 76 will also be deected to a slight degree, wherein it may resiliently urge the prong to return to its initial position, as required in devices of this type.

I wish it to be understood that I do not consider the invention limited to the exact details of structure disclosed in the instant application, for obvious modifications will occur to those skilled in the art to which the invention pertains.

I claim:

1. In a grounded electrical plug having a plug body, at least one power prong secured within said body and projecting outwardly thereof, and a grounding prong pivotally mounted upon said plug body, the improvement comprising: said plug body having a hollow bore Itherein, the axis of which is substantially perpendicular to the axis of said power prong, said grounding prong having a first elongated rectilinear portion arranged for rotation within said bore, and a second elongated portion disposed at an angle with respect to said first portion, and extending in a direction generally parallel to the axis of said power prong; said plug body having a recess in an outer surface thereof, a free end of said first portion of said grounding prong extending into said recess, said free end having a surface thereon lying in a plane parallel to the axis of said first portion, and resilient means disposed within said recess and bearing upon said surface to urge said grounding prong to a predetermined position.

2. In a grounded electrical plug having a plug body, at least one power prong secured within said body and projecting outwardly thereof, and a grounding prong pivotally mounted upon said plug body, the improvement comprising: said plug body having a hollow bore therein, the axis of which is substantially perpendicular to the axis of said power prong, said grounding prong having a first elongated rectilinear portion arranged for rotation within said bore, and a second elongated portion disposed at an angle with respect to said first portion, and

extending in a direction generally parallel to the axis of said power prong; said plug body having a recess in an outer surface thereof, a free end of said first portion of said grounding prong extending into said recess, said free end having a surface thereon lying in a plane parallel to the axis of said first portion, and resilient means disposed within said recess and bearing upon said surface to urge said grounding prong to a predetermined position; said resilient means including a continuous length of wire resiliently maintained within said recess by contact with side surfaces of said recess.

3. In a grounded electrical plug having a plug body, at least one power prong secured Within said body and projecting outwardly thereof, and a grounding prong pivotally mounted upon said plug body, the improvement comprising: said plug body being of molded resilient material having a bore therein, the axis of which is substantially perpendicular to the axis of said power prong, said grounding prong having a first elongated rectilinear portion arranged for rotation within said bore, and a second elongated portion disposed at an angle with respect to said first portion, and extending in a direction generally parallel to the axis of said power prong; said plug body having a recess in an outer surface thereof, a free end of said first pontion of said grounding prong extending into said recess, said free end having a surface thereon lying in a plane parallel to the axis of said first portion, and resilient means disposed within said recess and bean ing upon said surface to urge said grounding prong to a predetermined position.

4. In a grounded electrical plug having a plug body, at least one power prong secured within said body and projecting outwardly thereof, and a grounding prong pivotally mounted upon said plug body, the improvement comprising: said plug body being of molded resilient material having a bore therein, the axis of which is substantially perpendicular to the axis of said power prong said grounding prong having a rst elongated rectilinear portion arranged for rotation within said bore, and a second elongated portion disposed at an angle with respect to said first portion, and extending in a direction generally parallel to the axis of said power prong; said plug body having a recess in an outer surface thereof, a free end of said first portion of said grounding prong extending into said recess, said free end having a surface thereon lying in a plane parallel to `the axis of said first portion, and resilient means disposed within said recess and bearing upon said surface to urge said grounding prong to a predetermined position; said resilient means including a continuous length of wire resiliently maintained within said recess by contact with side surfaces of said recess.

References Cited in the file of this patent FOREIGN PATENTS 

1. IN A GROUNDED ELECTRICAL PLUG HAVING A PLUG BODY, AT LEAST ONE POWER PRONG SECURED WITHIN SAID BODY AND PROJECTING OUTWARDLY THEREOF, AND A GROUNDING PRONG PIVOTALLY MOUNTED UPON SAID PLUG BODY, THE IMPROVEMENT COMPRISING: SAID PLUG BODY HAVING A HOLLOW BORE THEREIN, THE AXIS OF WHICH IS SUBSTANTIALLY PERPENDICULAR TO THE AXIS OF SAID POWER PRONG, SAID GROUNDING PRONG HAVING A FIRST ELONGATED RECTILINEAR PORTION ARRANGED FOR ROTATION WITHIN SAID BORE, AND A SECOND ELONGATED PORTION DISPOSED AT AN ANGLE WITH RESPECT TO SAID FIRST PORTION, AND EXTENDING IN A DIRECTION GENERALLY PARALLEL TO THE AXIS OF SAID POWER PRONG; SAID PLUG BODY HAVING A RECESS IN AN OUTER SURFACE THEREOF, A FREE END OF SAID FIRST PORTION OF SAID GROUNDING PRONG EXTENDING INTO SAID RECESS, SAID FREE END HAVING A SURFACE THEREON LYING IN A PLANE PARALLEL TO THE AXIS OF SAID FIRST PORTION, AND RESILIENT MEANS DISPOSED WITHIN SAID RECESS AND BEARING UPON SAID SURFACE TO URGE SAID GROUNDING PRONG TO A PREDETERMINED POSITION. 